JP3555759B2 - Display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display device, and more specifically, to improvement of a display element suitable for a display using an organic EL element.
[0002]
[Background Art]
An organic EL element generally has a laminated structure in which an organic EL light emitting layer is sandwiched between electrodes. One electrode is a metal such as Al, and the other electrode is light transmission by ITO (Indium Tin Oxide) or the like. Transparent electrode. Of course, light output from the organic EL light emitting layer is directly output from the transparent electrode side, but light output to the metal electrode side is reflected by the metal electrode and output to the transparent electrode side. In a display device using such an organic EL element, light that enters the organic EL light emitting layer from external light via the transparent electrode is also reflected on the metal electrode side and output from the transparent electrode side. That is, external light is added to the light that forms the original image by the organic EL light emitting layer. For this reason, the contrast of an image is reduced in the presence of external light, for example, in the daytime.
[0003]
As a conventional technique for improving such a decrease in contrast, there is a display element disclosed in Japanese Patent Application Laid-Open No. 9-127885. This has a configuration in which a circularly polarizing means combining a linear polarizing plate and a quarter-wave plate is provided on the light emitting surface side of the display device. Since the circular polarization direction of the incident light from the outside and the circular polarization direction reflected on the display device side are opposite, the external light is blocked by the circular polarization means. Further, Japanese Patent Application Laid-Open No. 2000-315558 describes an organic EL device in which a visible light absorbing layer is provided between a cathode electrode, which is a metal electrode, and an organic EL light emitting layer.
[0004]
Furthermore, by simply arranging color filters of R (red), G (green), and B (blue) transmission on the R, G, and B light-emitting pixels, reflection of external light other than light-emitting colors can be reduced. It can be suppressed . However, this method does not reduce external light reflection for the original emission colors of R, G, and B. For this reason, the contrast will still decrease. As such a conventional technique, there is an organic EL display device disclosed in JP-A-2000-3786. According to this, a G color filter having a main peak wavelength of light transmittance of 490 to 530 nm is disposed in the G organic light emitting layer.
[0005]
[Problems to be solved by the invention]
However, the above background art has the following disadvantages.
{Circle around (1)} In the display device of JP-A-9-127885, although the effect of suppressing external light reflection is great, the transmittance of light from the original organic EL light emitting layer is also reduced, and the luminance is reduced to 50% or less. .
{Circle around (2)} In the organic EL device disclosed in Japanese Patent Application Laid-Open No. 2000-315558, since the light of the organic EL light emitting layer is also absorbed by the light absorbing layer, the brightness is also reduced to 50% or less.
(3) The background art of applying the R, G, and B light transmission filters to the R, G, and B pixels, respectively, is an effective method, but the external light reflectance is about 30%, and the reduction effect is small. Not enough.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a display device and a display device which can significantly reduce a decrease in contrast due to external light without causing a decrease in luminance of an original image. An object of the present invention is to provide a method for preventing a decrease in contrast.
[0007]
The display device according to the present invention is a display device in which R (red), G (green), and B (blue) pixels are arranged in a predetermined order, and one of R, G, and B is selected. A filter that absorbs light of one color is arranged on the light output side or the outside light incident side of the other unselected color pixel, and an optical resonator is provided corresponding to each color pixel area. The configuration is such that the reflectance of the color is minimized.
[0008]
One of the main modes is characterized in that the filter is an absorption filter for G light , which is arranged on the light output side or the outside light incidence side of the R and B pixels. In another embodiment, each of the R, G, and B pixels has a structure in which an organic EL layer is sandwiched between a reflective layer and a transparent layer, and the filter is connected to the light output side or the external light incident side of the transparent layer. It is characterized by being arranged in. In still another embodiment, each of the R, G, and B pixels has a structure in which an organic EL layer is sandwiched between a reflective layer and a translucent reflective layer, and the filter is connected to the light output side of the translucent reflective layer. Alternatively, it is characterized in that it is arranged on the outside light incident side.
[0009]
The method for preventing a decrease in contrast of a display device according to the present invention is a method for preventing a decrease in contrast of a display device in which R (red), G (green), and B (blue) pixels are arranged in a predetermined order. A color having the highest luminous reflectance among G and B is selected, and a transmission filter of a corresponding color is arranged on a light output side or an external light incidence side of a pixel of a color other than the selected color , An optical resonator is provided corresponding to each color pixel area, the optical resonator is configured so that the reflectance of the color is minimized, and the optical output side or the external light incident side of the pixel of the selected color is By not arranging a transmission filter, a reduction in contrast due to external light is prevented.
[0010]
In the display device according to the present invention, the filter that absorbs light of one color selected from R, G, and B is disposed on the light output side or the external light incident side of the other unselected color pixels. And an optical resonator is provided corresponding to each color pixel area, and the optical resonator is configured so that the reflectance of the color is minimized. Is suppressed, and the overall contrast is improved. In particular, by setting the selected color to G (green) having a high luminous reflectance by the naked eye, the contrast is further improved.
Further, in the method for preventing a decrease in contrast of a display device according to the present invention, a color having the highest luminous reflectance among R, G, and B is selected, and a light output side or outside of a pixel of a color other than the selected color is selected. On the light incident side, a transmission filter of the corresponding color is arranged , and an optical resonator is provided corresponding to each color pixel area, and the optical resonator is configured so that the reflectance of the color is minimized and selected. Since the transmission filter is not disposed on the light output side or the outside light incidence side of the pixel of the different color, a decrease in contrast due to outside light is prevented.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment First, a first embodiment of the present invention will be described in detail. As shown in FIG. 1A, the display device has a configuration in which R, G, and B light-emitting pixels are two-dimensionally arranged in a fixed order. In the illustrated example, the pixels are arranged in a repetition order of R, G, B,... In the X direction, and light-emitting pixels of the same color are continuous in the Y direction. Then, an image pixel P is formed by a combination of the light-emitting pixels R, G, and B that are continuous in the X direction. In the present embodiment, the G light absorbing filters FG are provided on the image display side (light output side or external light incident side) of the R and B light emitting pixels excluding the G light emitting pixel.
[0012]
FIG. 2 shows a stacked structure of the R or B light emitting pixel. Referring to FIG. 1, a reflective layer 12 also serving as an anode electrode is formed on a glass substrate 10 by using Pt, Au, Cr, W, or the like. Next, a buffer layer 14 is laminated on the reflective layer 12 by m-MTDATA, 2-TNATA or the like, and a hole transport layer 16 is further laminated thereon by α-NPD or the like. On the hole transport layer 16, a light emitting layer 18 also serving as an electron transport layer is laminated by Alq3 or the like. The organic EL layer 20 is composed of the buffer layer 14, the hole transport layer 16, and the light emitting layer 18.
[0013]
Next, on the organic EL layer 20, a translucent reflective layer 22 also serving as a cathode electrode is formed by lamination using Mg: Ag (an alloy of Mg and Ag). A passivation film 26 made of SiN or the like is formed on the translucent reflective layer 22 via a transparent conductive film 24 made of ITO or the like. On the passivation film 26, the above-mentioned G light absorption filter FG is arranged.
[0014]
When the preferred thickness of each of the above layers is shown,
{Circle around (1)} Reflecting layer 12: 100 to 300 nm,
{Circle around (2)} Buffer layer 14: 15 to 300 nm;
(3) Hole transport layer 16: 15 to 100 nm,
{Circle around (4)} Light-emitting layer 18: 15 to 100 nm;
{Circle over (5)} Translucent reflective layer 22: 5 to 50 nm,
{Circle around (6)} Transparent conductive film 24: 30 to 1000 nm;
{Circle around (7)} Passivation film 26: 500-10000 nm,
It is.
[0015]
Next, the operation of such a light-emitting pixel will be described. Of the light emitted from the light-emitting layer 18 of the organic EL layer 20, part of the light passes through the translucent reflective layer 22 as shown by an arrow F1, and furthermore, The light passes through the transparent conductive film 24 and the passivation film 26 and enters the G light absorption filter FG. However, a part of the light emitted from the light emitting layer 18 is reflected by the translucent reflective layer 22 and the reflective layer 12, respectively, as indicated by the arrow F2. That is, an optical resonator structure is formed by the translucent reflective layer 22 and the reflective layer 12, whereby light causes multiple interference. This acts as a kind of narrow band filter, and the half width of the spectrum of the extracted light is reduced, so that the color purity is improved.
[0016]
For this purpose, the peak wavelength of the narrow-band filter is made to coincide with the peak wavelength of the spectrum of the light to be extracted. That is, the optical distance between the reflective layer 12 and the translucent reflective layer 22 is L (the optical film thickness of the organic EL layer 20), and the reflected light generated between the translucent reflective layer 22 and the reflective layer 12 Is Φ (rad), and λ is the peak wavelength of the spectrum of the light to be taken out of the light emitted from the organic EL layer 20.
2L / λ + Φ / (2π) = m (m is an integer) (1)
To satisfy the conditions. In this equation (1), L and λ may have the same unit, for example, “nm”. Actually, it is set so as to be within the range satisfying the expression (1) and the optical distance L of the optical resonator becomes a positive minimum value.
[0017]
Such a condition corresponds to a condition for generally maximizing the light transmittance. Conversely, it is a condition for minimizing the reflection of light incident from the outside. Here, paying attention to the external light, the external light reflectance R (λ) of the luminescent pixel when there is no G light absorption filter FG is as shown in FIG. In the figure, the graphs of R, G, and B show the external light reflectance in each of the R, G, and B light emitting pixels. As described above, the optical resonator has a condition that minimizes external light reflection. This state is as shown in FIG. 3. For example, in the case of the luminescent pixel of B, reflection of external light of B (around 450 to 500 nm) is minimized. The R and G light emitting pixels are also as illustrated.
[0018]
On the other hand, the visibility curve y (λ) representing the sensitivity of the naked eye is as shown in FIG. Therefore, to the naked eye, the external light reflectance R (λ) shown in FIG. 3 is multiplied by the visibility curve y (λ) shown in FIG. 4, as shown in a graph shown in FIG. Referring to FIG. 5, the external light reflectance at the emission peak wavelength is suppressed to a very low value of about several percent. For example, the external light reflectance of B of the B light emitting pixel is substantially 0%. The R and G light emitting pixels are also as illustrated. However, as shown by an arrow F5 (wavelength 550 nm), the external light reflectance of G in the R light emitting pixel is 0.6, and the external light reflectance of G in the B light emitting pixel is about 0.4. , Which are all quite large values.
[0019]
On the other hand, in the present embodiment, as shown in FIG. 1, the G light absorbing filter FG is provided on the R and B light emitting pixels. The transmission characteristic T (λ) of the G light absorption filter FG is set, for example, as shown in FIG. That is, the transmittance in the wavelength region of G light having high visibility to the naked eye (see FIG. 4) is minimized, and the transmittance of other R and B lights is maximized. In other words, G light is almost absorbed, and R and B light is almost transmitted.
[0020]
The external light passes through the G light absorption filter FG having such characteristics when entering and exiting the luminescent pixel. For this reason, the external light reflectance Rt (λ) when the G light absorbing filter FG is arranged in the R and B light emitting pixels is the same as the external light reflectance R (λ) shown in FIG. Rt (λ) = T (λ) × R (λ) × T (λ) obtained by multiplying the transmission characteristic T (λ) of the G light absorbing filter FG twice (2)
Given by This is shown in a graph in FIG. 7, and the external light reflectance in the G band of the light emitting pixel of each color can be kept very low.
[0021]
Further, as described above, the visibility curve y (λ) of the naked eye is as shown in FIG. Accordingly, the external light reflectance Re (λ) of the present embodiment in consideration of the visibility curve y (λ) is:
Re (λ) = Rt (λ) × y (λ) (3)
This is shown in a graph in FIG.
[0022]
And external light reflectance of the present embodiment applying the G light absorbing filter (Fig. 8), compared external light reflectance when not using the G light absorbing filter (Fig. 5), first, the light emission pixels of G The graphs are identical. Next, comparing the graphs of the R and B luminescent pixels, FIG. 8 shows that the external light reflectance is much lower over the entire visible region. In particular, the wavelength significantly decreases in the wavelength region of G near the wavelength of 550 nm, and the reflection of external light is suppressed very effectively.
[0023]
Next, the ratio of the value obtained by integrating the external light reflectance to the value obtained by integrating the luminosity curve y (λ) over the entire visible region is the luminous reflectance, as shown in FIG. In the figure, first, when the G light absorption filter of the present embodiment is used, the ratio of the value obtained by integrating the external light reflectance Re (λ) of the above-described equation (3) to the luminosity integral value is shown. As shown, R emission pixels... 3.6, G emission pixels... 15.9, B emission pixels... 8.2, average. On the other hand, in the case without the G light absorption filter shown in FIG. 5, R light emitting pixels 47.5, G light emitting pixels 15.9, B light emitting pixels 32.0, average 31. 8 As described above, the luminous reflectance when the G light absorption filter is provided is 1/3 or less on average compared to the case where the G light absorption filter is not provided. Note that the luminous reflectance of the G light emitting pixel is the same value because the G light absorbing filter is not provided.
[0024]
On the other hand, the transmittance of the organic EL layer 20 for the original light emission is given by the transmission characteristic T (λ) of the G light absorption filter FG shown in FIG. For this reason, the reduction in the original light extraction efficiency is small, and the reduction in the brightness of the display image is minimized. Therefore, according to the present embodiment, the contrast under external light can be significantly improved as compared with the related art without causing a decrease in display luminance.
[0025]
Next, as shown in FIG. 9, the luminous reflectance in the case of a three-color filter in which R, G, and B light emitting pixels are respectively provided with R, G, and B light transmission filters is shown in FIG. As shown in the figure, R emission pixels... 5.1, G emission pixels... 5.5, B emission pixels... 1.3, average... 4.0, which are even lower than this embodiment. It is the luminous reflectance. However, the method of using the three-color filter requires three types of materials to be used as the filters and also requires three times of patterning, resulting in a very high cost. On the other hand, in the present embodiment, only one type of material for the G light absorbing filter FG is required, and patterning is performed only once, so that it is possible to improve production efficiency and reduce manufacturing cost.
[0026]
In addition, as a modified example of the present embodiment, there is an example shown in FIGS. First, the example of FIG. 1B is an example in which R light absorbing filters FR are provided for G and B light emitting pixels. In this case, the reflectance in the wavelength region of the R light in the graph of the external light reflectance in FIG. 5 is reduced. The example in FIG. 1C is an example in which B light absorbing filters FB are provided for R and G light emitting pixels. In this case, the reflectance in the wavelength range of the B light in the graph of the external light reflectance in FIG. 5 is reduced.
[0027]
Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The same reference numerals are used for the same or corresponding components as in the first embodiment. In the present embodiment, light is extracted from the substrate side, which is opposite to the above embodiment. The transparent conductive film 24, the translucent reflection layer 50 of Cr or the like, the buffer layer 14, the hole transport layer 16, a light emitting layer 18, and a reflective layer 52 of Al or the like are stacked in this order. That is, the substrate side has a translucent reflective layer 50 configuration. The G light absorption filter FG is further disposed on the substrate 10.
[0028]
Part of the light emitted from the light emitting layer 18 of the organic EL layer 20 is transmitted through the translucent reflective layer 50 as shown by the arrow F11, and further transmitted through the transparent conductive film 24 and the substrate 10 to absorb G light. The light enters the filter FG. However, part of the light emitted from the light emitting layer 18 is reflected by the translucent reflective layer 50 and the reflective layer 52, respectively, as indicated by the arrow F12. That is, an optical resonator structure is formed by the translucent reflection layer 50 and the reflection layer 52, which causes multiple interference of light. In any case, the light output from the substrate 10 is output to the outside via the G light absorption filter FG. According to the second embodiment, the same effect as that of the first embodiment can be obtained.
[0029]
Third Embodiment Next, a third embodiment will be described with reference to FIG. First, the example of FIG. 11A is an example in which the G light absorption filter FG is provided on the passivation film 26. The example of FIG. 3B is an example in which a G light absorption filter FG is formed between the transparent conductive film 24 and the passivation film 26. In each case, only the position of the G light absorption filter FG is different from that of the first embodiment. Next, while the light emitting layer 18 of the first embodiment has a structure also serving as an electron transport layer, the example of FIG. 2C separates them, and the light emitting layer 18A and the electron transport layer 18B are formed. Have been.
[0030]
Each of the above examples includes a reflective layer and a translucent reflective layer, and these constitute an optical resonator structure. On the other hand, in the example of FIG. 11D, there is no translucent reflective layer, and the light output from the organic EL layer 20 directly enters the G light absorbing filter FG as shown by the arrow F1, or As shown by F3, there is no optical resonator that is reflected by the reflection layer 12 and enters the G light absorption filter FG. The present invention is also applicable to a general organic EL device using such a reflective electrode (reflective layer 12) and a transparent electrode (transparent conductive film 24). In this case, for example, there are organic EL elements so as to improve the chromaticity by using a band-pass filter as in Japanese Patent Laid-Open No. 6-132081, the G light absorbing filter as in the present example R and B The same effect can be obtained by using the above-mentioned luminescent pixels. According to this example, there is an advantage that the type of material and the number of times of patterning can be reduced as compared with the organic EL device disclosed in JP-A-6-132081.
[0031]
Embodiment 4 Next, Embodiment 4 will be described with reference to FIG. In this example, among the R, G, and B light emitting pixels, an R light transmitting filter ER is provided on an R light emitting pixel, and a B light transmitting filter EB is provided on a B light emitting pixel. In other words, this is an example in which the G light filter is excluded from the background art using the R, G, and B color filters. In other words, the G light absorption filter described above can be considered as a transmission filter for R and B light . On the other hand, as shown in FIG. 9, the luminous reflectance when the R light transmitting filter is applied to the R light emitting pixel is as low as 5.1, and the B light transmitting filter is applied to the B light emitting pixel. In this case, the luminous reflectance is very low at 1.3.
[0032]
Therefore, as shown in FIG. 1 (D), R, R to each light emitting pixel of the B, B of the transmission filter ER light, EB and by providing each, as shown in FIG. 9, the luminous reflectance, R ... 5.1, G... 15.9, B... 1.3, and the average is 7.4, so that a result superior to the above embodiment can be obtained.
[0033]
<Other Embodiments> The present invention has many embodiments, and various modifications can be made based on the above disclosure. For example, the following is also included.
(1) In the above embodiment, the present invention is applied to an organic EL display. However, the R, G, and B pixels may be of any type. For example, the present invention is applicable to various pixel matrix displays such as a liquid crystal display and a plasma display. Further, various configurations and materials also the organic EL devices are known, may be applied to any of them.
(2) The materials and film thicknesses of the above-described portions are also examples, and may be changed as needed.
[0034]
【The invention's effect】
As described above, the present invention has the following effects.
(1) Since only one of R, G, and B is used as a filter for external light, the type of material and the number of times of patterning during production are reduced.
(2) Since the G light absorption filter is provided on the light output side or the outside light incidence side of the R and B pixels, the contrast is greatly improved, and the type of material and the number of times of patterning during production are reduced. It is reduced and productivity is improved.
(3) In particular, since the organic EL element having the optical resonator is used as the pixel, the luminance does not decrease.
(4) Since R and B light transmission filters are arranged on the light output side or the outside light incidence side of the R and B pixels, the outside light is well absorbed by them and the contrast is greatly improved. I do.
[Brief description of the drawings]
FIG. 1 is a plan view showing an overlapping state of a luminescent pixel and a filter in an embodiment according to the present invention.
FIG. 2 is a main cross-sectional view illustrating an example of a stacked structure of a light-emitting pixel.
FIG. 3 is a graph showing external light reflectance in a case where there is no G light absorption filter in the embodiment.
FIG. 4 is a graph showing a visibility curve of the naked eye.
FIG. 5 is a graph showing an external light reflectance of the embodiment in consideration of visibility.
FIG. 6 is a graph showing the transmittance of the G light absorbing filter in the embodiment.
FIG. 7 is a graph showing external light reflectance in consideration of a G light absorption filter in the embodiment.
8 is a graph showing the external light reflectance in FIG. 7 in consideration of the visibility shown in FIG.
FIG. 9 is a diagram illustrating the relationship between the presence or absence of a filter and luminous reflectance in each of R, G, and B light emitting pixels.
FIG. 10 is a sectional view showing a main laminated structure according to a second embodiment of the present invention.
FIG. 11 is a sectional view showing a main laminated structure according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Substrate 12 ... Reflection layer 14 ... Buffer layer 16 ... Hole transport layers 18 and 18A ... Emitting layer 18B ... Electron transport layer 20 ... Organic EL layer 22 ... Semi-transparent reflective layer 24 ... Transparent conductive film 26 ... Passivation film 50 ... Semi- Transparent reflective layer 52 Reflective layer FB B light absorbing filter FG G light absorbing filter FR R light absorbing filter ER R light transmitting filter EB B light transmitting filter L Optical distance P Image pixels R, G, B: Light emitting pixel

Claims (13)

A display device in which R (red), G (green), and B (blue) pixels are arranged in a certain order,
A filter that absorbs light of one color selected from the above R, G, and B is disposed on the light output side or outside light incident side of the other unselected color pixels, and is provided in each color pixel area. A display device , wherein an optical resonator is provided correspondingly, and the optical resonator is configured such that the reflectance of the color is minimized . 2. The display device according to claim 1, wherein the filter is an absorption filter for G light, and is disposed on the light output side or the outside light incidence side of the R and B pixels. Each of the R, G, and B pixels has a structure in which an organic EL layer is sandwiched between a reflective layer and a transparent layer, and the filter is arranged on the light output side or the external light incident side of the transparent layer. The display device according to claim 2, wherein: Each of the R, G, and B pixels has a structure in which an organic EL layer is interposed between a reflective layer and a translucent reflective layer, and the filter is disposed on the light output side or the external light incident side of the translucent reflective layer. The display device according to claim 2, wherein the display device is arranged. The display device according to claim 4, wherein the reflection layer and the translucent reflection layer form an optical resonator for extracting light desired to be extracted by the pixel. The phase shift of the reflected light generated in the optical resonator is Φ (rad), the optical distance between the reflective layer and the translucent reflective layer is L (nm), and the peak wavelength of the light spectrum to be extracted is λ (nm). ) And each value is
2L / λ + Φ / 2π = m (m is an integer)
6. The display device according to claim 5, wherein the display device is designed to satisfy the following condition. 7. The display device according to claim 6, wherein the optical distance L of the optical resonator is set to be a positive minimum value. A method for preventing a decrease in contrast of a display device in which R (red), G (green), and B (blue) pixels are arranged in a predetermined order,
A color having the highest luminous reflectance among the R, G, and B is selected, and a transmission filter of a corresponding color is provided on the light output side or outside light incidence side of a pixel other than the selected color. In addition to the arrangement, an optical resonator is provided corresponding to each color pixel region, the optical resonator is configured so that the reflectance of the color is minimized, and the light output side or outside of the pixel of the selected color is provided. A method for preventing a decrease in contrast of a display device, wherein a decrease in contrast due to external light is prevented by disposing the transmission filter on a light incident side. An R light transmission filter is disposed on the light output side or the external light incident side of the R pixel, and a B light transmission filter is disposed on the light output side or the external light incident side of the B pixel. 9. The method according to claim 8, wherein no filter is arranged on the light output side or the outside light incidence side of the G pixel. Each of the R, G, and B pixels has a structure in which an organic EL layer is sandwiched between a reflective layer and a translucent reflective layer. 10. The method according to claim 9, wherein the contrast is reduced. 11. The method according to claim 10, wherein the reflection layer and the translucent reflection layer constitute an optical resonator for extracting light desired to be extracted from the pixel. The phase shift of the reflected light generated in the optical resonator is Φ (rad), the optical distance between the reflective layer and the translucent reflective layer is L (nm), and the peak wavelength of the light spectrum to be extracted is λ (nm). ) And each value is
2L / λ + Φ / 2π = m (m is an integer)
12. The method according to claim 11, wherein the display device is designed to satisfy the following condition. 13. The method according to claim 12, wherein the optical distance L of the optical resonator is set to be a positive minimum value.

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